196

~;TOMATOLOGY

Degenerative changes in primary trigeminal axons and in neurons in nucleus caudalis following tooth pulp extirpations in the cat. -- S. Gobel and J.M. Binck, Brain Res., 132 (1977) 347--354

The removal of infected tooth pulps results in destruction of the receptor endings of small myelinated and unmyelinated axons innervating the pulp chambers of teeth. Subsequent filling of the chamber with inert materials precludes any regeneration of these endings. This paper demonstrates with EM techniques that tooth pulp extirpations in cat result in degenerative changes in the central terminations of these primary trigeminal neurons and i:~ the neurons tb .~y synapse on in the marginal (layer I ) a n d substantia gelatinosa (layers I! and #:II) layers of nucleus caudalis. The degenerating primary endings in layer I show a blackened axoplasm and are rapidly phago- cytosed by glial cells. Their rapid degeneration parallels the disappearance of anmyelinated axons from the spinal V tract and suggests that they are the +.erminals of these unmyelinated axons. Primary endings in layers II and III, on the other hand, degenerate in situ over a longer time period, gradually losing their synaptic vesicles and synaptic connections. Their gradual degen- eration parallels the protracted degeneration of primary myelinated axons in the spinal V tract, suggesting they are connected to myelinated axons. In summary, these experiments indicate major primary afferent and transsynap- tic degenerative changes following tooth pulp removal. It is possible that such changes play ~ role in oral-facial pathological pain conditions ill humans.

Location of feline tfigeminal ganglion cells innervating maxillary canine teeth: a horserad:~sh peroxidase analysis. -- K.V. Anderson and H.S. Rosing, Exp. Neurol., 57 (1977) 302--306

This study exarnired the ~omatotopical organization of cell bodies in the trigeminal ganglion connected to per,:pheral afferents innervating maxillary canine teeth in cat. Horseradish peroxidase (HRP) wa~ injected into exposed too~;h pulps on one s~de and its transport to ganglion cells was examined 24-- 72 h later. HRP granules were observed in cells of ipsilateral and contralat- erai ganglia. Mos;~ cells containing HRP were of small to medium size (less than 4,3 /~m). Label~cl cells were distributed throughout the maxillary por- tion of the ganglia ,~.,ith greater numbers found h~ the ventral regions. No HRP cells were observed in control animals. Th~s report of transmedian innervation of feline canine teeth is of considerable interest and is consistent wi.~!~ other reports usi~ig different anatomical and physiological methods.

The o1~gin of h~ipulses recorded ~orn dentinal cavities in the tooth of the cat.--G, i-hegers~am, Acta physiol, scand., 97 (1976) 121--128

Evidence is presented that single unit discharges recorded from dentinal cavities in teeth erigfna~e from nerve fibers in the tooth pulp. Voltage differ- ences measured betwee~, two cavities in cat canine teeth appear to originate